Filters are used in a wide variety of applications where it is desired to separate particles or other substances from a fluid stream (e.g., a stream of gas). Applications of filters include removing dust and other particulates in residential or commercial ventilation systems. Applications further include removing substances from flue gases such as those from cement kilns, coal and oil fired power generation plants, industrial boilers, municipal waste incinerators, and oil refinery plants. Such flue gases may contain substantial varieties and quantities of environmental pollutants, such as sulfur oxides (SO2 and SO3), nitrogen oxides (NO and NO2), mercury (Hg) vapor, and particulate matters (PM). In the United States, burning coal alone generates about 27 million tons of SO2 and 45 tons of Hg each year.
The destructive effects of various pollutants on human health and on the ecosystem have long been recognized. For example, SOx and NOx have been linked to the outbreak of respiratory diseases in affected areas. They also form acid rain, which damages forests, fisheries, and architectures. As for Hg, it is a potent toxin to the nervous system. Exposure to mercury can affect the brain, spinal cord, and other vital organs. It is particularly dangerous to developing fetuses and young children.
Enacted and proposed environmental regulations require significant reductions in mercury emissions in a short time frame. These regulations extend to different industries; presenting challenges in various types of facilities (e.g., cement kilns).
In U.S. Pat. No. 7,442,352, which is incorporated herein by reference in its entirety, a process is described for reducing multiple pollutants (e.g., sulfur oxides, mercury vapor, and fine particulate matters). In that process, pollutants are removed by modules, which contain a microporous adsorbent material (i.e., sorbent) held within a polymer matrix. The mercury vapor is removed from flue gas by chemically adsorbing Hg vapors (e.g., either elemental mercury or oxidized mercury) into the polymer matrix. A sorbent house is described in U.S. Pat. No. 7,442,352 that comprises a plurality of sorbent modules, each comprised of a solid frame and a plurality of sheets held in place by the solid frame.